Table size

Consider the following:

Large row length:

For sequentially accessed tables that have a large row length because of many columns (100 or more), you may improve performance by dividing the tables into several smaller ones, or by creating a view. This assumes that your application is not accessing all of the columns. The main reason for the better performance is that I/O may be reduced because you will get more rows per page. Splitting the table will affect applications that access all of the columns because they will incur the overhead of joining the table back together again. You must decide where to split the table based on the nature of the application and frequency of access to various columns.

Large number of rows:

If a table has a large number of rows and the queries that access the table always specify a WHERE clause, create an index over the columns that are used in the WHERE clause. The index will allow the Db2® for i optimizer to use the index to access the table. The use of indexes is very important for achieving the best possible performance.